The present invention relates generally to mobile telecommunications systems utilizing a subscriber information module, and in particular, the present invention relates to a method and apparatus for remote multiple access to services of a subscriber identity module card by multiple subscriber devices in a GSM system.
In a Global System for Mobile Communications (GSM) system and in other telecommunications systems, a mobile device includes hardware and software specific to a radio interface, along with subscriber specific data located in a subscriber identity module, or xe2x80x9cSIMxe2x80x9d. The SIM can either be a smart card having physical dimensions similar to the well-known size of credit cards, or alternately can be xe2x80x9ccutxe2x80x9d to a much smaller format, commonly referred to as a xe2x80x9cplug-in SIMxe2x80x9d. In either case, the SIM card contains and organizes information, such as identity information identifying the subscriber as a valid subscriber, subscriber supplied information, such as telephone numbers, for example, operator specific information, and a certain subset of mobility management state information, such as information about the last public land mobile network in which the mobile device was registered. In this way, when inserted within a mobile device in a cellular network, the SIM card enables the mobile device to be personalized, or associated with subscriber specific information. However, once the SIM card is removed, the mobile device cannot be used, except, if permitted by the network, for emergency related transmissions.
FIG. 1 (Prior Art) is a schematic diagram of known system architecture of a SIM card interface within a mobile device. As illustrated in FIG. 1, a SIM card 100 interfaces with a software component portion 102 of a mobile device through an electrical interface 104 that is coupled to a SIM physical data interchange layer 106 of software component portion 102. Software component portion 102 also includes a SIM authentication and ciphering unit 108, a SIM command/response interface 110, and a SIM physical presence detection unit 112.
Commands corresponding to authentication and ciphering requests that are received and transmitted internally by the mobile device are converted by SIM command/response interface 110 to a standardized command format. The standardized command is then transmitted to SIM authentication and ciphering unit 108 for authentication and cipher key generation, and is then transmitted to SIM physical data interchange layer 106. Commands corresponding to requests other than authentication and ciphering requests that are received and transmitted internally by the mobile device are converted by SIM command/response interface 110 to a standardized command format, and the standardized command is then transferred directly to physical data interchange layer 106. Physical data interchange layer 106 formats the standardized command received from either SIM authentication and ciphering unit 108 or directly from SIM command/response interface 110 into physical data according to GSM required electronic signals and transmission protocols. The physical data is then transmitted from SIM physical data interchange layer 106 to SIM card 100 through electrical interface 104.
Upon receiving the command, SIM card 100 subsequently transmits physical data corresponding to a response to the command from SIM card 100 to physical data interchange layer 106, through electrical interface 104. Physical data interchange layer 106 formats the physical data into a standardized response. The standardized response, if made in response to an authentication and ciphering command, is transmitted to SIM authentication and enciphering unit 108 for authentication and cipher key generation, and then to SIM command/response interface 110, which converts the: standardized response to a format required internally by the mobile station. Standardized responses to commands corresponding to requests other than authentication and ciphering requests are transmitted directly from physical data interchange layer 106 to SIM command/response interface 110, which converts the standardized response to a format required internally by the mobile device.
Throughout the internal command and response generation process described above, electrical interface 104 continuously transmits a physical presence signal to a physical presence detection unit 112 to indicate that SIM card 100 is inserted and is in electrical contact with electrical interface, and that SIM card 100 is functioning properly. Once the physical presence signal is interrupted, such as when SIM card 100 has been removed or fails, and is therefore no longer detected by physical presence unit 112, physical presence detection unit 112 transmits an interrupt signal indicating the absence of SIM card 100, and service access to the mobile device is interrupted.
The SIM card, as defined by GSM specifications, has been further enhanced in terms of information organization and functionality for use with other services. For example, work for the Telecommunications Industry Association/Electronics Industry Association (TIA/EIA) 136 Enhanced General Packet Radio Services (EGPRS) for TIA/EIA 136 proposes the use of the European GSM SIM card plus enhancements for use by the American time division multiple access (TDMA) proposed high-speed wireless data service. The current GSM definition of the SIM card will likely be expanded to include other services as well, such as third generation mobile voice and data services.
One of the disadvantages that will result as the SIM card is utilized in more and more subscriber devices, is that a separate SIM card will be required for use in each subscriber device, and therefore a user of multiple SIM card enabled devices will be required to utilize a multiple number of SIM cards. Accordingly, what is needed is a method and apparatus that enables multiple SIM card enabled subscriber devices to be utilized using a single SIM card.